What good is 2 PCIe x16 slots when only one runs at x16?

a video card using a PCIe x 16 slot is faster than the video port built in on the motherboard true or false?

Likewise, PCIe x16 refers to a Gen 4 expansion card or slot with a 16-lane configuration And so on Each new PCI Express generation doubles

pcie slot gpu 3 x PCIe Gen5x4 2 x PCIe Gen5x4 1 x PCIe Gen5x4 PCIe x16 3 x PCIe x16 2 x PCIe x16 1 x PCIe x16 PCIe x16 5 x PCIe

pcie slot configuration gen1 gen2 gen3 2 SSD, Support PCIe x4 x8 x16 Slot USB Type C ·